Question

我想制作一个屏幕截图并将其显示在我的程序窗口中，但到目前为止我只能将屏幕设为白色。

我做错了什么？

代码：

#include <windows.h>


LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("screen") ;
     HWND         hwnd ;
     MSG          msg ;
     WNDCLASS     wndclass ;

     wndclass.style         = CS_HREDRAW | CS_VREDRAW ;
     wndclass.lpfnWndProc   = WndProc ;
     wndclass.cbClsExtra    = 0 ;
     wndclass.cbWndExtra    = 0 ;
     wndclass.hInstance     = hInstance ;
     wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION);
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
     wndclass.lpszMenuName  = NULL ;
     wndclass.lpszClassName = szAppName ;

     if (!RegisterClass (&wndclass))
     {
          MessageBox (NULL, TEXT ("Program requires Windows NT!"), 
                      szAppName, MB_ICONERROR) ;
          return 0 ;
     }

     hwnd = CreateWindow (szAppName, TEXT ("Digital Clock"),
                          WS_POPUP|WS_DLGFRAME|WS_VISIBLE, //WS_OVERLAPPEDWINDOW| WS_MAXIMIZE,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          NULL, NULL, hInstance, NULL) ;

     ShowWindow (hwnd, SW_MAXIMIZE);// iCmdShow) ;
     UpdateWindow (hwnd) ;

     while (GetMessage (&msg, NULL, 0, 0))
          {
          TranslateMessage (&msg) ;
          DispatchMessage (&msg) ;
          }
     return msg.wParam ;
     }



LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     static BOOL   f24Hour, fSuppress ;
     static HBRUSH hBrushRed ;
     static int    cxClient, cyClient ;
     HDC           hdc ;
     PAINTSTRUCT   ps ;
     TCHAR         szBuffer [2] ;
   HGDIOBJ hMem;  // HBITMAP hMem;  
  HDC compdc;

     switch (message)
     {
     case WM_CREATE:
          hBrushRed = CreateSolidBrush (RGB (255, 0, 0)) ;
    keybd_event(VK_SNAPSHOT, 0, KEYEVENTF_EXTENDEDKEY, 0); //get screen snapshot into clipboard
    OpenClipboard(NULL); 
    hMem = GetClipboardData(CF_BITMAP);   

   case WM_SETTINGCHANGE:

          return 0 ;

     case WM_SIZE:
          cxClient = LOWORD (lParam) ;
          cyClient = HIWORD (lParam) ;
          return 0 ;

     case WM_TIMER:
          InvalidateRect (hwnd, NULL, TRUE) ;
          return 0 ;

     case WM_PAINT:
          hdc = BeginPaint (hwnd, &ps) ;
   compdc = CreateCompatibleDC(hdc);
          SelectObject(compdc,hMem);
    BitBlt(hdc,0,0,cxClient,cyClient,compdc,20,20,SRCCOPY);

          EndPaint (hwnd, &ps) ;
          return 0 ;
     case WM_KEYDOWN:
     switch(wParam)
     {
     case VK_ESCAPE:
                  DeleteObject (hBrushRed);
                 PostQuitMessage (0) ;
     }

     case WM_DESTROY:

          DeleteObject (hBrushRed) ;
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}

Answer 1

首先，我会避免像这样使用剪贴板 - 用户应该只有在明确剪切或复制后才能看到剪贴板中的更改。

相反，您应该直接捕获屏幕的内容。鉴于您使用原始Win32调用进行此操作，您首先要在WndProc中定义一些额外的变量：

static HBITMAP bmp;
static RECT r;

然后在你的WM_CREATE处理程序中，你有类似这样的代码来实际捕获屏幕：

{
// First get a DC to the entire screen.
    HDC s = GetDC(NULL);

// Then get the size of the screen:
    r.left = GetSystemMetrics(SM_XVIRTUALSCREEN);
    r.right = GetSystemMetrics(SM_CXVIRTUALSCREEN);
    r.top = GetSystemMetrics(SM_YVIRTUALSCREEN);
    r.bottom = GetSystemMetrics(SM_CYVIRTUALSCREEN);

// Then create a bitmap to hold the picture of the screen:
    bmp = CreateCompatibleBitmap(s, r.right, r.bottom);

// Create a memory DC and select that BMP into it:
    HDC mem=CreateCompatibleDC(s);
    HBITMAP old = (HBITMAP)SelectObject(mem, bmp);

// Copy the bits from the screen to our DC (and our BMP that's selected into it.
    BitBlt(mem, 0, 0, r.right, r.bottom, s, 0, 0, SRCCOPY);

// Clean up:
    SelectObject(mem, old);
    DeleteDC(mem);
    ReleaseDC(NULL, s);
}
break;

然后在你的WM_PAINT处理程序中，你有这样的代码将它绘制到你的窗口：

{
    hdc = BeginPaint(hWnd, &ps);

// Create a compatible DC and select our BMP into it:
        HDC mem=CreateCompatibleDC(hdc);
        HBITMAP old = (HBITMAP)SelectObject(mem, bmp);

// Copy bits from our BMP to our window:
        BitBlt(hdc, 0, 0, r.right, r.bottom, mem, 0, 0, SRCCOPY);

// Clean up:
        SelectObject(hdc, old);
        DeleteDC(mem);
    EndPaint(hWnd, &ps);
    break;
}

如何拍摄屏幕并在VC ++中显示？

代码：

1 个答案: